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The bar effect in the galactic gas motions traced by 6.7 GHz methanol maser sources with VERA

Published online by Cambridge University Press:  24 July 2012

Naoko Matsumoto  and
Mareki Honma
Naoko Matsumoto
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, Japan email: naoko.matsumoto@nao.ac.jp
Mareki Honma
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, Japan email: naoko.matsumoto@nao.ac.jp Department of Astronomical Science, The Graduate University of Advanced studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo, Japan email: mareki.honma@nao.ac.jp
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Abstract

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To establish the existence of the galactic bar, ten methanol maser sources around the starting points of the spiral arms were observed with VERA (VLBI Exploration of radio astrometry) using the phase-referencing technique at 6.7 GHz band. For six out of ten sources, absolute proper motions were obtained with better than 3σ accuracy. Using VLBI 3-D data of eight sources, including our five sources, we compared the observed data with three galactic models and found that the model including the bar effect is better to explain the 3-D data, than a flat circular rotation model. A non-flat circular rotation model is also consistent with the VLBI data. Based on a dynamical model with a bar, we estimate an inclination angle of the bar around 35°, which is consistent with previous studies.

Keywords

masersGalaxy: kinematics and dynamicsradio lines: ISM
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S287: Cosmic Masers - from OH to H0 , January 2012 , pp. 419 - 420
Copyright
Copyright © International Astronomical Union 2012

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